/*
 * Copyright (C) 2007 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.dialectek.blackguard;

import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.CharBuffer;
import java.nio.FloatBuffer;

import javax.microedition.khronos.opengles.GL10;

/**
 * A 2D rectangular mesh. Can be drawn textured or untextured.
 *
 */
class Grid {
   public Grid(int w, int h)
   {
      if ((w < 0) || (w >= 65536))
      {
         throw new IllegalArgumentException("w");
      }
      if ((h < 0) || (h >= 65536))
      {
         throw new IllegalArgumentException("h");
      }
      if (w * h >= 65536)
      {
         throw new IllegalArgumentException("w * h >= 65536");
      }

      mW = w;
      mH = h;
      int       size       = w * h;
      final int FLOAT_SIZE = 4;
      final int CHAR_SIZE  = 2;
      mVertexBuffer = ByteBuffer.allocateDirect(FLOAT_SIZE * size * 3)
                         .order(ByteOrder.nativeOrder()).asFloatBuffer();
      mTexCoordBuffer = ByteBuffer.allocateDirect(FLOAT_SIZE * size * 2)
                           .order(ByteOrder.nativeOrder()).asFloatBuffer();

      int quadW      = mW - 1;
      int quadH      = mH - 1;
      int quadCount  = quadW * quadH;
      int indexCount = quadCount * 6;
      mIndexCount  = indexCount;
      mIndexBuffer = ByteBuffer.allocateDirect(CHAR_SIZE * indexCount)
                        .order(ByteOrder.nativeOrder()).asCharBuffer();

      /*
       * Initialize triangle list mesh.
       *
       *     [0]-----[  1] ...
       *      |    /   |
       *      |   /    |
       *      |  /     |
       *     [w]-----[w+1] ...
       *      |       |
       *
       */

      {
         int i = 0;
         for (int y = 0; y < quadH; y++)
         {
            for (int x = 0; x < quadW; x++)
            {
               char a = (char)(y * mW + x);
               char b = (char)(y * mW + x + 1);
               char c = (char)((y + 1) * mW + x);
               char d = (char)((y + 1) * mW + x + 1);

               mIndexBuffer.put(i++, a);
               mIndexBuffer.put(i++, b);
               mIndexBuffer.put(i++, c);

               mIndexBuffer.put(i++, b);
               mIndexBuffer.put(i++, c);
               mIndexBuffer.put(i++, d);
            }
         }
      }
   }


   void set(int i, int j, float x, float y, float z, float u, float v)
   {
      if ((i < 0) || (i >= mW))
      {
         throw new IllegalArgumentException("i");
      }
      if ((j < 0) || (j >= mH))
      {
         throw new IllegalArgumentException("j");
      }

      int index = mW * j + i;

      int posIndex = index * 3;
      mVertexBuffer.put(posIndex, x);
      mVertexBuffer.put(posIndex + 1, y);
      mVertexBuffer.put(posIndex + 2, z);

      int texIndex = index * 2;
      mTexCoordBuffer.put(texIndex, u);
      mTexCoordBuffer.put(texIndex + 1, v);
   }


   public void draw(GL10 gl, boolean useTexture)
   {
      gl.glEnableClientState(GL10.GL_VERTEX_ARRAY);
      gl.glVertexPointer(3, GL10.GL_FLOAT, 0, mVertexBuffer);

      if (useTexture)
      {
         gl.glEnableClientState(GL10.GL_TEXTURE_COORD_ARRAY);
         gl.glTexCoordPointer(2, GL10.GL_FLOAT, 0, mTexCoordBuffer);
         gl.glEnable(GL10.GL_TEXTURE_2D);
      }
      else
      {
         gl.glDisableClientState(GL10.GL_TEXTURE_COORD_ARRAY);
         gl.glDisable(GL10.GL_TEXTURE_2D);
      }

      gl.glDrawElements(GL10.GL_TRIANGLES, mIndexCount,
                        GL10.GL_UNSIGNED_SHORT, mIndexBuffer);
      gl.glDisableClientState(GL10.GL_VERTEX_ARRAY);
   }


   private FloatBuffer mVertexBuffer;
   private FloatBuffer mTexCoordBuffer;
   private CharBuffer  mIndexBuffer;

   private int mW;
   private int mH;
   private int mIndexCount;
}
